This invention relates generally to gas generation and more particularly to the generation of hydrogen gas and its isotopes.
Currently convenient, storable, inexpensive sources of predetermined quantities of hydrogen for inflation of balloons, fluidic devices, fuel cells, chemical-laser systems and mechanical power sources are needed. It is necessary that the hydrogen generation is fast (&gt;10 l/sec), the hydrogen so produced has as low a temperature as possible and the generating means is as light as possible. Pressurized hydrogen gas cylinders cannot meet the severe weight-volume restrictions of many applications. Hydrogen-gas generation by conventional chemical reactions, for example, the reaction of a metal or metal hydride with an acid, base, water, or alcohol is not adequate for many applications for the above reasons. In addition, most of these reactions are highly exothermic, and the reaction mixtures must be cooled to prevent boiling off of the liquid phase and formation of a hydrogen/(alcohol or water) vapor mixture).
The best results to date have been obtained from the reactions disclosed in U.S. Pat. Nos. 3,734,863; 3,862,052; 3,931,395; 3,977,990; and 4,022,705 to Beckert et al. More specifically, U.S. Pat. Nos. 3,734,863; 3,862,052; and 3,931,395 disclose reacting ammonium or hydrazinium salts with suitable complex metal hydrides as expressed by the following general formulae and general equations: ##EQU1## where X is an acid group, such as halides (Cl.sup.-, Br.sup.-, F.sup.-) or sulfate (SO.sub.4.sup.2-); n is the valency of the acid group; Y is a mono- or divalent metal capable of forming complex hydrides, such as alkali and alkaline earth metals, especially lithium, sodium, potassium, magnesium, barium, calcium or strontium; m is the valency of said metal, and Z is a trivalent metal capable of forming complex hydrides, such as, boron or aluminum. Similarly, U.S. Pat. No. 3,977,990 to Beckert et al. teaches that hydrogen-gas-evolution rates and gas temperatures of certain hydrogen-gas-generating compositions are modified by adding compounds, e.g., LiAlH.sub.4, which thermally decompose in the reaction zone producing hydrogen while lowering the reaction temperature; and certain metal acetylacetonates, metal oxides, and the like which, when added in relatively small amounts accelerate or decelerate the hydrogen gas evoluation rate.
While these methods and compositions are satisfactory in providing hydrogen at a fast rate from solid, storable compositions, complex metal hydrides are commercially available only to a limited extent and they are relatively expensive. Furthermore, many of these compositions produce hydrogen at an unacceptably high temperature. One attempt in overcoming the expense and limited availability of many of the above compositions is disclosed and described in U.S. patent application Ser. No. 916,423 now U.S. Pat. No. 4,231,891 of Beckert et al. These compositions comprise a hydrazinium or an ammonium salt and certain metals. While providing cheaper hydrogen at a purity sufficient for laser or fuel cell applications, the compositions produce hydrogen at temperatures that are unacceptably high for many applications.